Single step multi-section exposure scanning method

ABSTRACT

A single step multi-section exposure scanning method for a scanner. The scanner includes a photo-sensor and a stepper motor. The photo-sensor has N rows of sensor cells that correspond to each primary color. The scanning device is driven forward an exposure distance for each revolution of the stepper motor. The single step multi-section exposure scanning method includes the following steps. First, the photo-sensor moves forward one exposure distance. One row of sensor cells is exposed after moving every 1/Nth of the exposure distance. Thereafter, analogue voltages obtained through the exposed row of sensor cells are transmitted to an analogue/digital converter. The above process is repeated until the entire document is scanned.

Notice: More than one reissue application has been filed for the reissueof U.S. Pat. No. 6,608,301 filed as application Ser. No. 09/920,388 onJul. 31, 2001.

The present application is a divisional of U.S. application Ser. No.11/208,129 filed Aug. 19, 2005, which in turn is a reissue of U.S.application Ser. No. 09/920,388 filed Jul. 31, 2001 now U.S. Pat. No.Re.42,033, all of which are assigned to the assignee of the presentinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning method. More particularly,the present invention relates to a single step multi-section exposurescanning method.

2. Description of Related Art

In general, a charge-coupled device (CCD) is used as the photosensitiveelement inside most color scanners. The color CCD is constructed using alarge number of sensor cells each capable of sensing light intensity ofone of the three primary colors including red (R), green (G) and blue(B). FIG. 1 is a schematic diagram of a conventional charge-coupleddevice (CCD). As shown in FIG. 1, the CCD includes a first row of sensorcells 102 and a second row of sensor cell 104 for detecting intensity ofthe primary color red (R), a third row of sensor cells 106 and a fourthrow of sensor cells 108 for detecting intensity of the primary colorgreen (G) and a fifth row of sensor cells 110 and a sixth row of sensorcell 112 for detecting intensity of the primary color (B). After aperiod of exposure, each sensor cell accumulates a definite amount ofelectric charges according to the intensity of light falling on theparticular sensor cell.

FIG. 2 is a schematic diagram showing a conventional scanning circuit ofa scanner. As shown in FIG. 2, a sensor 202 converts the electriccharges accumulated inside the CCD (not shown) into an analogue voltagesignal. Through an analogue/digital converter 204, the analogue voltagesignal is converted to a digital voltage signal. Thereafter, anapplication specific integrated circuit 206 initiates a computation ofthe compensation value supplied from a compensation RAM unit 210 and thedigital voltage signal. The computed video signal is transferred to avideo RAM unit 208 for storage. In a subsequent step, the applicationspecific integrated circuit 206 reads out video signal data from thevideo RAM unit 208 and transmits the video signal data to aninput/output port 212.

Resolution of a scanner is an important parameter for judging thequality of a scanner. However, the production of a high-resolutionscanner often causes some critical problems including: (1)lamp-adjusting techniques have to be deployed to resolve sensorsaturation problem because long exposure will lead to saturation of theCCD while short exposure will lead to insufficient time for outputtingvoltage signal; (2) using a run-stop-scan scanning method to scan adocument not only leads a repetition of start, rotate and stop motionfor the stepper motor, but also leads to a slow down of scanning speed;(3) the CCD generates a large quantity of voltage signal data so thatstorage capacity of the compensation memory has to increase, therebyrestricting large area scanning for obtaining a higher resolution; (4)the generation of large quantity of voltage signal data by the CCD alsonecessarily increases the storage capacity of the video RAM unit.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a singlestep multi-section exposure scanning method capable of reducingcompensation memory and video memory capacity and does not rely onlamp-adjusting techniques to solve sensor saturation problem.Ultimately, hardware production and engineering cost is reduced andfewer compensation counters are used. Furthermore, a larger areascanning to support a high image resolution is possible and the scannercan have a higher scanning speed.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, theinvention provides a single step multi-section exposure scanning methodfor a scanner. The scanner includes a photo-sensor and a stepper motor.The photo-sensor has N rows of sensor cells that correspond to eachprimary color. The scanning device is driven forward an exposuredistance for each revolution of the stepper motor. The single stepmulti-section exposure scanning method includes the following steps.First, the photo-sensor moves forward one exposure distance. One row ofsensor cells is exposed after moving every 1/Nth of the exposuredistance. Thereafter, analogue voltages obtained by the exposed row ofsensor cells are transmitted to an analogue/digital converter. The aboveprocess is repeated until the entire document is scanned.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

FIG. 1 is a schematic diagram of a conventional charge-coupled device(CCD);

FIG. 2 is a schematic diagram showing a conventional scanning circuit ofa scanner; and

FIG. 3 is a schematic diagram showing a single step multi-sectionexposure scanning method according to one preferred embodiment of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

In one embodiment of this invention, the scanner has a photo-sensor anda stepper motor. The charge-coupled device (CCD) inside the photo-sensoris capable of sensing three primary colors red (R), green (G) and blue(B). Furthermore, each primary color is sensed by N rows sensor cells(refer to FIG. 1, N=2, 3, . . . ). In general, the photo-sensor movesforward a distance L (that is, the distance a scanning head moves over ascan document) when the stepper motor rotates once. During thisinterval, the N rows of sensor cells for each primary color must detectintensity of light reflected from a strip of scan document having awidth.

FIG. 3 is a schematic diagram showing a single step multi-sectionexposure scanning method according to one preferred embodiment of thisinvention. When the scan document is at position Y (can be the beginningor any position of the scan document), one rotation of the stepper motoris equivalent to moving the scan document from the position Y to a newposition Y+L/N. While the stepper motor rotates, if position Y is at thebeginning of the scan document, the first row of sensor cells picks upreflected light from the document. However, if position Y is not at thestarting point of scanning, the Nth row of sensor cells converts theaccumulated charges resulting from light absorption into analoguevoltage signals. The analogue voltage signals are transferred to ananalogue/digital converter 204 (as shown in FIG. 2) (S302).

The stepper motor continues to rotate bringing the scan document fromposition Y+L/N to a new position Y+2L/N. While the stepper motorrotates, the second row sensor cells picks up light reflected from thescan document. The first row sensor cells convert the accumulatedcharges resulting from light absorption into analogue voltage signals.The analogue voltage signals are transferred to the analogue/digitalconverter 204 (as shown in FIG. 2) (S304).

The stepper motor continues to run so that the sensor cells sequentiallyabsorb reflected light from the scan document and submit analoguevoltage signals until the scan document moves from position Y+(N−1)L/Nto position Y+NL/N. While the stepper motor rotates, the Nth row sensorcells pick up reflected light from the scan document and the (N−1)th rowsensor cells convert the accumulated charges resulting from lightabsorption into analogue voltage signals. The analogue voltage signal istransmitted to the analogue/digital converter 204 (shown in FIG. 2)(S306). In other words, each time the stepper motor completes arotation, accumulated electric charges resulting from light absorptionby the N rows of sensor cells are converted to an analogue voltagesignal and transmitted to the analogue/digital converter 204 (shown inFIG. 2).

After the Nth row of sensor cells detects intensity of light reflectedfrom the scan document, the scanner decides if that is the end of thescanning operation (that is, the scanner has scanned to the end of thedocument) (S308). If scanning is not yet complete, current position(position Y plus motor rotation distance L) is chosen as the initialposition (Y=Y+L) (S310) of the next rotation. Step S302 is executedagain. On the other hand, if scanning is complete, accumulated electriccharges resulting from light absorption by the Nth row sensor cells areconverted to analogue voltage signals and transmitted to theanalogue/digital converter 204 (as shown in FIG. 2).

For a scanner having a staggered CCD design, two rows of light sensorsare used for detecting intensity of each primary color. Hence, theaforementioned single step multi-section exposure scanning method has anN equal 2 for this type of scanner.

Since intensity of light reflected from the document is sensed by a rowof sensors, the effect of exposure time is minimized. Because saturationproblems no longer have to be resolved by implementing lamp-adjustingtechniques, hardware and engineering cost is reduced. After detectingthe reflected light from the scan document by the Nth row of sensors(N=1, 2, 3, . . . ), the accumulated charges due to light falling on the(N−1)th row of sensors are converted to analogue voltage signal.Thereafter, the analogue voltage signal is transferred to theanalogue/digital converter 204 (as shown in FIG. 2). Theanalogue/digital converter 204 converts the analogue voltage signalsinto digital voltage signals. A computation of the digital voltagesignals with a compensation value submitted from the compensation memoryunit 210 is carried out inside the application specific integratedcircuit 206. Since the amount of data undergoing compensationcomputation inside the application specific integrated circuit 206 comesfrom a row of sensors, storage capacity of the compensation memory unitand the number of compensation counters required for computation aregreatly reduced. Hence, a larger area can be scanned to obtain a higherresolution. Video signals obtained from compensation computation insidethe application specific integrated circuit 206 are transferred to thevideo RAM unit 208 for temporary storage. The application specificintegrated circuit 206 is also responsible for reading out video datafrom the video RAM unit 208 and sending the data to the input/outputport 212. Using a run-and-scan scanning method, the stepper motor canrotate continuously without repetitive starts and stops. Ultimately,scanning speed of the scanner is increased.

In summary, major advantages of this invention includes:

-   -   1. There is no need to apply lamp-adjusting techniques to        minimize sensor saturation problem. Hence, hardware and        engineering cost is reduced.    -   2. Storage capacity of the compensation memory unit as well as        the number of compensation counters required to conduct        computation is reduced. Thus, large area scanning can be        conducted to obtain a higher resolution.    -   3. Using a run-and-scan scanning method, the stepper motor can        run continuously leading to a higher scanning speed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A single step multi-section exposure scanning method for a scannerhaving a photo-sensor and a stepper motor, wherein the photo-sensor usesN rows of sensors to process each one of a plurality of primary colorsand the stepper motor drives the photo-sensor an exposure distance L forone step of the stepper motor, the scanning method comprising the stepsof: moving an exposure distance along a scan document; exposing a row ofnot yet exposed sensor cells after moving each 1/Nth of the exposuredistance L; sending out an analogue voltage obtained from a previous rowof sensors when the next row of sensors is exposed; and repeating theabove steps until the entire document is scanned, whereby for one stepof the stepper motor moving the exposure distance L, N sequential timesof exposure with respect to the N rows for the primary color areperformed.
 2. The scanning method of claim 1, wherein the value of N is2.
 3. The scanning method of claim 1, wherein the photo-sensor is ableto detect light intensity of all three primary colors including red (R),green (G) and blue (B).
 4. The scanning method of claim 3, wherein thephoto-sensor uses a staggered charge-coupled device to detect lightintensity of the primary colors red (R), green (G) and blue (B).
 5. Thescanning method of claim 3, wherein the row of sensor cells use theaccumulated electric charges produced according to light intensity togenerate analogue voltages.
 6. A scanner, comprising: a photo sensorincluding N rows of sensor cells, wherein each row of sensor cells isconfigured to process light corresponding to a different primary color;means for moving at least one of the photosensor and a scan document anexposure distance L, the movement to change a position of thephotosensor relative to the scan document; and means for exposing a rowof not yet exposed sensor cells after moving each 1/Nth of the exposuredistance L; wherein the scanner is configured to repeat movement andexposure until at least a portion of the scan document is scanned,wherein for each movement, N sequential times of exposure with respectto the N rows for the primary color are performed.
 7. The scanner ofclaim 6, wherein the value of N is
 2. 8. The scanner of claim 6, whereinthe photosensor is configured to detect light intensity of all threeprimary colors including red (R), green (G) and blue (B).
 9. The scannerof claim 8, wherein the photosensor includes a staggered charge-coupleddevice configured to detect light intensity of the primary colors red(R), green (G) and blue (B).
 10. The scanner of claim 8, wherein eachrow of sensor cells uses the accumulated electric charges producedaccording to light intensity to generate analogue voltages.
 11. Thescanner of claim 6, wherein the photosensor includes a charge-coupleddevice.
 12. A scanner, comprising: a photosensor having N rows of sensorcells to process each one of a plurality of primary colors; a steppermotor configured to drive at least one of the photosensor and a scandocument an exposure distance L for one step of the stepper motor; and amachine readable memory storing instructions that, if executed, resultin: moving at least one of the photosensor and the scan document theexposure distance L, the movement to change a position of thephotosensor relative to the scan document; exposing a row of not yetexposed sensor cells after moving each 1/Nth of the exposure distance L;and repeating the moving and the exposing until at least a portion ofthe scan document is scanned, wherein for one step of the stepper motor,N sequential times of exposure with respect to the N rows for theprimary color are performed.
 13. The scanner of claim 12, wherein thevalue of N is
 2. 14. The scanner of claim 12, wherein the photosensor isconfigured to detect light intensity of the primary colors including red(R), green (G) and blue (B).
 15. The scanner of claim 14, wherein thephotosensor includes a staggered charge-coupled device configured todetect light intensity of the primary colors red (R), green (G) and blue(B).
 16. The scanner of claim 14, wherein each row of sensor cells usesthe accumulated electric charges produced according to light intensityto generate analogue voltages.
 17. The scanner of claim 12, wherein thephotosensor includes a charge-coupled device.